We are considering starting an indoor show to a retail property for one season before it moves into a more permanent location. It's in a nice place but is part of a strip mall, with the usual dull and uninteresting fronts next to a tuxedo shop and a Subway. Not the best place but, as I mentioned, it's a temp location until our permanent location is available in 2014.

Any suggestions on signage and tricking out the front? I don't want just a banner - that looks cheap - so hopefully can find some way to spruce things up and build interest. Any suggestions?

I'd talk to the building owner and find out what they'll allow, then do as much as you can. You might be able to have a basic sign up during normal hours, but when you're open make more of an entry way to the haunt that spills out into the sidewalk. You might even be able to have your ticket booth outside, which would help save on space inside and helps draw attention outside. If you're limited to just a sign, I'd get the best 3D sign above the door as you can (which can be expensive unless you foam carve it) and dress up the windows.

You may already have plans in place for your design but here is my suggestion:
At any themed attraction, the experience begins for the guest as soon as they get out of the car. When we were confined to a strip mall in 2011 we themed the whole thing as a medical clinc. A clinic is believable as far as being in a strip mall.
I hate getting out of my car at a strip mall then walking inside to see a "cemetery" when I can look up to see ceiling tiles.
This is jut my opinion. We didn't need (or could even afford) a big fancy facade because it was a clinic. We had built in window displays and decorated them heavily to fit the theme of the show.
So perhaps theme the show to the environment. Hospital/clinic, mental institution, chemical research facility, Resident Evil-type stuff, etc... All could fit in the urban brick-and-mortar atmosphere of a commercial space and be fairly believable.